The invention relates to the trimming of integrated circuits. In particular, the invention relates to the trimming of integrated circuits using fuse circuitry, while minimizing the amount of die area consumed by the fuse circuitry.
During the manufacturing of integrated circuits, process variations can result in variations in electrical characteristics of the circuitry. A technique known as trimming is typically used to compensate for process variations. After the circuit manufacturing, various components of the integrated circuit are adjusted, or trimmed, to bring the electrical characteristics within permitted parameters. For example, trimming can be used to adjust resistances or capacitances, to adjust transconductance values, and to correct for DC offsets produced by process variations.
One trimming technique makes use of fuse circuitry, which is incorporated into the integrated circuit. Based upon a functional measurement of the integrated circuit performed by probing the wafer during an initial wafer test, the need for trimming is identified. Selected fuses are then blown to make the necessary adjustments to the integrated circuit.
Fuse circuits used for device trimming require fuse probe pads and wide metal lines to accommodate the large currents which are necessary for fuse blowing. The large physical size of these fuse components, compared to their simple function, contributes disproportionally to the die size. This is undesirable because the fuse components take up a significant amount of die area that could otherwise be allocated to other useful circuits, or allow a smaller die to be used.
In an attempt to counteract this disproportionate use of die area by fuse circuitry, design rules have attempted to compact the fuse circuitry, and the number of fuses used in an integrated circuit is typically limited. However, fuse component sizes and the associated design rules still dictate large die area usage, and minimizing the number of trim fuses hampers a designer's ability to assign the optimum number of trim circuits.